System and method for transmitting messages between transceivers using electromagnetically coupled signals

ABSTRACT

A communication system and method for communicating over a wire in a group of wires are described. The communication system includes a first transceiver connected to a first wire in the group of wires and a second transceiver connected to a second wire in the group of wires. Although not directly connected by a wire, the transceivers communicate with each other using electromagnetically coupled signals. For example, the first transceiver transmits signals over the first wire that produce interference on the second wire. The second transceiver detects the interference on the second wire and transmits a communication signal over the second wire that electromagnetically couples to the first wire. The electromagnetically coupled signal conveys a message to the first transceiver that induces the first transceiver to produce a response. The message directs the first transceiver to take an action that adjusts the produced interference. The communication signal has a predefined frequency and phase characteristic that causes the first transceiver to recognize the message.

RELATED APPLICATION

[0001] This application claims the benefit of and filing date of U.S.Provisional Application, Serial No. 60/144,562, filed Jul. 16, 1999,entitled “Inter-Telephone Wire Communication Via ElectromagneticallyCoupled Signals,” and is a divisional of copending U.S. patentapplication Ser. No. 09/616,954, filed Jul. 14, 2000 entitled “A SystemAnd Method For Transmitting Messages Between Transceivers UsingElectromagnetically Coupled Signals,” both of which are incorporated byreference herein.

FIELD OF THE INVENTION

[0002] The invention relates in general to communications, and morespecifically to a method and system for communicating betweentransceivers using electromagnetically coupled signals.

BACKGROUND OF THE INVENTION

[0003] Standard telephone wire connections between homes and telephonecentral offices are configured in binder groups with ten to fiftytwisted pair wires per binder group. Binder groups are combined to formmulti-pair cables that can have from ten to several thousand twistedpairs. These multi-pair cables have a metallic electrical sheathing andplastic covering that shield the twisted pairs from most noise and otherdisturbances that exist outside of the binder group in the air orunderground. As a result, the twisted pair binder group is atransmission environment that can be significantly impacted by noiseresulting from signals that are transmitted on one twisted pair leaking,or “crosstalking”, into another twisted pair in the same binder groupvia electromagnetic energy coupling. The unwanted electromagnetic energythat couples into a twisted pair from signals transmitted on other pairsin the same binder group is called crosstalk noise, or simply“crosstalk”. In most cases, this crosstalk is one of the limitingfactors for the performance of all the transmission systems that arecontained in a particular binder group. When crosstalk is the primaryfactor, the transmission environment is called a crosstalk-limitedenvironment. One of the most problematic types of crosstalk forcommunicating data over telephone wires is near-end crosstalk, which iscrosstalk that results from transmitters that are “near” the receiver,i.e., at the same end of the wire. For example, near-end crosstalk for areceiver in a home (customer premise, CP) originates from otherneighboring homes' transmitters. This crosstalk is typically the mostsevere type because in this case the transmitter is closest to thereceiver and therefore the magnitude of the crosstalk can be large.

[0004] One technique for decreasing the levels of near-end crosstalk inthe telephone binder group transmission environment is by maintainingfrequency separation between the receiving signal and the near-endcrosstalking signal. In general, techniques or processes that areintended to decrease the levels of crosstalk in multi-pair metallic loopcables are known as “spectrum management” plans. The American NationalStandards Institute (M4SI) is currently drafting an American Standard onSpectrum Management called “Spectrum Management for Loop TransmissionSystems”. This standard will, among other things, set rules on whichfrequency bands transceivers should use depending on whether they arelocated at the CP or the central office (CO). By implementing a spectrummanagement plan that dictates the frequency bands for transmission fromthe CO to the CP (downstream transmission) and separate frequency bandsfor transmission from the CP to the CO (upstream direction), one cansignificantly decrease the near-end crosstalk in the binder group.

[0005] Telephone companies intend to establish spectrum management plansbased on the ANSI standard for their loop plan for this reason. However,even though such companies hope to enforce the rules of such a plan onnew transceivers deployed in their network, little can be done aboutolder “legacy” systems that may not follow these rules.

[0006] Furthermore, the spectrum compatibility problem is morecomplicated because in some homes people use their in-home telephonewiring for other transmission systems. One example of an in-home wiringtransmission system is a home computer networking system that is used toconnect multiple computer devices in people's homes. This transmissionsystem, also known as home phone networking (HPN), does not follow thespectrum management rules that the telephone companies want to use intheir network. As a result, HPN signals that “leak” from homes onto thetelephone network become a severe near-end crosstalk source for manytelephone company-deployed services. This problem of spectrum pollutionfrom signals that do not follow the spectrum management rules is seriousand affects the availability of high-speed data access to homes andbusinesses. Thus, there remains a need for a system and method that canreduce the crosstalk interference encountered by transceiverscommunicating on wires in a binder group.

SUMMARY OF THE INVENTION

[0007] In one aspect, the invention features a method for use by atransceiver to communicate over a wire in a group of wires. In themethod, communications are received over a first wire and transmits acommunication signal over the first wire. The communication signaltransmitted over the first wire electromagnetically couples to a secondwire to produce an electromagnetically coupled signal on the secondwire. The electromagnetically coupled signal conveys a message thatinduces a response from a second transceiver connected to the secondwire.

[0008] The conveyed message directs the second transceiver to alter anoperation of the second transceiver. More specifically, one embodimentof the method detects interference on the communications received overthe first wire and the transmission of the communication signal occursin response to detecting the interference. The transmission of thecommunication signal occurs if the detected interference exceeds apredetermined threshold. In a further embodiment, the detectedinterference is crosstalk.

[0009] In another aspect, the invention features a method forcommunicating between a first and second transceiver that are connectedto different wires in a group of wires. The first and secondtransceivers are not connected to each other by any wire in the group ofwires. One embodiment of the method transmits signals by a firsttransceiver over a first wire. The first transceiver receives acommunication signal over the first wire. The communication signal istransmitted from a second transceiver over a second wire and iselectromagnetically coupled to the first wire from the second wire. Themethod further includes performing an action in response to a messageconveyed by the electromagnetically coupled communication signal.

[0010] In one embodiment, the performed action is an adjustment to atransmission parameter. The adjustment changes a power level used totransmit signals over the first wire. In another embodiment, theadjustment changes a frequency band used to transmit signals over thefirst wire. In yet another embodiment, the adjustment changes timeincrements used to transmit signals over the first wire.

[0011] In a further embodiment, the method includes receiving a secondelectromagnetically coupled signal over the first wire in response tothe adjustment to a transmission parameter. The adjustment of thetransmission parameter is stopped in response to the secondelectromagnetically coupled signal.

DESCRIPTION OF THE DRAWINGS

[0012] The aspects of the invention presented above and many of theaccompanying advantages of the present invention will become betterunderstood by referring to the included drawings, in which:

[0013]FIG. 1 is a diagram illustrating an embodiment of a communicationsystem in which communication occurs between a two transceivers usingelectromagnetically coupled signals;

[0014]FIG. 2 is a diagram illustrating an embodiment of a HPN networkinducing interference into digital subscriber line (DSL) transceiverconnection;

[0015]FIG. 3 is a diagram illustrating an embodiment of a DSLtransceiver using electromagnetically coupled signals to communicatewith HPN devices that are interfering with the communications of the DSLtransceiver; and

[0016]FIG. 4 is a flowchart illustrating an embodiment of a process usedby the HPN and DSL transceivers to communicate with electromagneticallycoupled signals to request a reduction in the interference.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIG. 1 shows a communication system 1 embodying the principles ofthe invention. The communication system 1 includes a first transceiver 2in electrical communication with another transceiver 2′ over a firstcommunication channel 4 and a second transceiver 15 in electricalcommunication with another transceiver 15′ over a second communicationchannel 8. Representative of each transceiver shown, the secondtransceiver 15 includes a receiver 12 and a transmitter 18. The firstcommunication channel 4 is within physical proximity of the secondcommunication channel 8 such that signals traversing either of thecommunication channels 4, 8 can electromagnetically couple to the othercommunication channel. In one embodiment, the communication channels 4,8 are separate twisted pair telephone wires within a single bindergroup.

[0018] In brief overview, the second transceiver 15 uses the fact thatsignals traversing one twisted pair in a binder group canelectromagnetically couple into other twisted pairs in the same bindergroup to send messages to other transceivers (e.g., transceiver 2)connected to those other twisted pairs. Such communication is hereafterreferred to as “inter-telephone wire communication”. It is to beunderstood that the wires 4, 8 do not need to be within a single bindergroup to practice the principles of the invention. It is sufficient thatthe wires 4, 8 be within physical proximity of each other to enable thesignals to electromagnetically couple from one wire to the other.

[0019] Inter-telephone wire communication can be employed for a varietyof purposes. One purpose, for example, is to decrease crosstalk in abinder group. During operation of the communication system 1, thetransceiver 2 transmits information 6, or signal transmissions, over thefirst communication channel 4 to communicate with the transceiver 2′.These signal transmissions 6 electromagnetically couple (arrow 16′) tothe second communication channel 8. The electromagnetically coupledsignal transmissions 10 may interfere with communications exchanged overthe second communication channel 8 between the transceivers 15, 15′. Ifthe transceiver 2 is near the transceiver 15 (e.g., at the same end of abinder group), the interference manifests as near-end crosstalk,described above. Similarly, signals originating from the transceiver 2′and transmitted over the communication channel 4 can also induce suchinterference on the second communication channel 8.

[0020] The receiver 12 of transceiver 15, which is connected to thesecond communication channel 8, receives the electromagnetically coupledsignal transmissions 10 and determines whether the interference causedby electromagnetically coupled signal transmissions 10, if any, is abovea predetermined threshold. If the interference is above the predefinedthreshold, the transmitter 18 transmits a signal 14 over the secondcommunication channel 8. In accordance with the principles of theinvention, this signal 14 provides a message that is understood by thetransceiver 2.

[0021] Although the transceivers 2, 15 are physically connected toseparate communication channels 4, 8, respectively, the presentinvention enables the transceiver 15 to send messages to transceiver 2.This communication occurs because the signal 14 that is transmitted onone communication channel (here, communication channel 8) creates anelectromagnetic field that surrounds nearby communication channels(e.g., communication channel 4) and induces voltages into the nearbycommunication channel (e.g., communication channel 4). Theelectromagnetic coupling is designated in FIG. 1 as arrow 16. The signal14 is electromagnetically coupled onto the first communication channel 4to produce a corresponding electromagnetically coupled message 19.Although the induced voltages are normally viewed as harmfulinterference, the electromagnetically coupled message 19 is produced forthe specific purpose of communicating with the source of theinterference (here, transceiver 2) and therefore is not consideredharmful.

[0022] Note that the signal 14 can electromagnetically couple to aplurality of wires and that each transceiver connected to such a wirecan receive the message 19. The message 19 requests that each receivingtransceiver (e.g., the transceiver 2) take appropriate actions to adjustthe interference 10 that the transceiver 2 is producing. Typically, therequest is to adjust a transmission characteristic that reduces theinterference, but in other embodiments, the message 19 could be sent forother purposes, e.g., to make adjustments that increase theinterference. Further, any communications via the electromagneticallycoupled message 19 to the transceiver 2 from a transmitter 18 is withinthe scope of the present invention. For example, in another embodimentthe message 19 is created to identify or exchange characteristics of thetransmission or service between the transceivers 2, 15. In yet anotherembodiment, the transceiver 15 issues the signal 14 (and correspondingelectromagnetically coupled message 19) to send data to the transceiver2.

[0023]FIG. 2 shows an embodiment of the communication system 1 shown inFIG. 1 that includes a home phone networking (HPN) system and a DSLsystem (ADSL, SDSL, VDSL or the like). DSL services are typicallyoffered by telephone companies and provide high speed data connectionsbetween a central office (CO) and homes and businesses. These DSLservices follow spectrum management rules, described above, in order todecrease crosstalk in the loop. HPN systems are in commerciallyavailable consumer personal computers (PCs). Such HPN systems generallydo not follow the spectrum management rules and therefore generate highlevels of crosstalk in the telephone network environment. In FIG. 2, theHPN system generates near-end crosstalk that affects the DSL system asdescribed below.

[0024] In more detail, a home 20 includes a home phone network (HPN) 24,which has several HPN transceivers 21, 22, 23 (generally 21) thatcommunicate with each other. The HPN 24 is also connected to a twistedpair of telephone wires 32. A second home 40 includes a DSL (e.g., DSL,ADSL, SDSL, VDSL, etc.) device 41 that communicates over a twisted pairof telephone wires 33 with a central office (CO), not shown. ADSLtransceivers have been standardized by ANSI in the T1.413 standard andby the International Telecommunications Union (ITU) in the G.992.1 andG.992.2 standards and the ITU is currently standardizing SDSL and VDSLsystems in projects called G.vdsl and G.shsdl.

[0025] Both twisted pairs 32, 33 are part of a binder group 30, whichhouses a plurality of twisted pair telephone wires. The HPN transceivers21 transmit HPN signals 26 that exit the home 20 onto the twisted pair32 and leak onto the other wires in the binder group 30 as crosstalknoise (shown as HPN crosstalk 31). The crosstalk 31 introduces anelectromagnetically coupled interference signal 35 over the twisted pair33. The DSL device 41 subsequently receives this interference signal 35.The reception of the interference signal 35 typically causes a decreasein the DSL service provided by the DSL device 41. It should be notedthat the interference signal 35 may not degrade the performance of theDSL device 41. Still, the interference signal 35 is unwanted and is notrecognized by the DSL device 41 as an expected signal. Therefore, theDSL device 41 uses inter-telephone wire communications described abovein FIG. 1 to communicate to the home 20 with the HPN 24. Again, as notedabove, inter-telephone wire communication uses the fact that signalstransmitted on one twisted pair in a binder group electromagneticallycouple to other twisted pairs in the same binder group.

[0026]FIG. 3 shows the DSL transceiver 41 communicating with the HPNtransceivers 21 via an electromagnetically coupled signal. Uponreception of the interference signal 35 (shown as shadow 35), the DSLdevice 41 determines if the interference signal 35 is above apredetermined threshold. In one embodiment, the DSL device 41 makes thisdetermination based on the amplitude of the interference signal 35. Inanother embodiment, the DSL device 41 bases this determination on theeffect that the interference signal 35 has on subsequent output. In yetanother embodiment, the DSL device 41 looks at the signal-to-noise ratioto aid in the determination.

[0027] In still yet another embodiment, the DSL device 41 determines ifthe interference signal 35 is at an acceptable level based on thecurrent operational status of the DSL device 41. In other words, the DSLdevice 41 varies the predetermined threshold as the type or importanceof its communications varies. For example, if the DSL device 41 is idleexcept for receiving the interference signal 35 (or any interference),the predetermined threshold can be set to a relatively high valuecompared to the predetermined threshold when the DSL device 41 isinvolved in a communication with another device. This enables thetransceivers 21 to operate without interruption from the DSL device 41if the DSL device 41 is not actively engaged in communication. Differentlevels of operational status can be incorporated into the DSL device 41to allow for variable predetermined thresholds, such as separatethresholds corresponding to when the DSL device 41 is inactive or whenthe DSL device 41 is performing a self-check.

[0028] If the interference signal 35 exceeds the predeterminedthreshold, the DSL device 41 transmits a High Crosstalk Detection (HCD)signal 44 on the twisted pair 33. The purpose of the HCD signal 44 is torequest that the HPN transceivers 21 adjust their transmissions so as toreduce or eliminate the interference signal 35 that the HPN transceivers21 are producing. In another embodiment, the HCD signal 44 has multiplepurposes including the adjustment of the interference signal 35. The HCDsignal 44 can have a purpose not related to interference in general orto the interference signal 35 in particular. Similar to theelectromagnetic coupling of the crosstalk 31 but in the oppositedirection, the HCD signal 44 is electromagnetically coupled onto thetwisted pair 32, as shown with the HCD signal arrow 62. Theelectromagnetic coupling of the HCD signal 44 introduces anelectromagnetically coupled signal 46. The HPN transceivers 21 thenreceive the electromagnetically coupled signal 46.

[0029] The HCD signal 44 is a known signal (i.e., a message understoodby the HPN transceivers 21) with predefined characteristics so that theHCD transceivers 21 can easily distinguish the HCD signal 46 from plaincrosstalk noise as well as other signals. In one embodiment, the HCDsignal 44 is a tone at 7.5 MHz, which is the center frequency of the HCDsignal 44 transmission. Other frequencies can be used to practice theinvention. In general, the selected tone frequency depends on the typeof transceivers with which the transceiver 15 wishes to communicate. TheHCD signal 44 can also be modulated with a known technique such asbinary-phase shift keying (BPSK), with alternating 180-degree phaseshifts. Similarly, the HCD signal 44 can be modulated with a techniquesuch as frequency-shift keying (FSK), with a different frequencycorresponding to each binary value.

[0030] The electromagnetically coupled signal 46 appears as a form ofcrosstalk to the HCN transceivers 21 because the electromagneticallycoupled signal 46 was electromagnetically coupled onto the twisted pair32 from another transmission source (here, the DSL device 41) on adistinct communication channel 33. However, each HPN transceivers 21 isconfigured to recognize a signal having the predefined characteristics,such as phase and frequency, described above as a predefined message.For example, upon detecting the electromagnetically coupled signal 46,the HPN transceivers 21 perform an action that in effect adjusts theamount of crosstalk 31 that is being electromagnetically coupled ontothe twisted pair 33.

[0031] In addition to electromagnetically coupling onto the twisted pair32, the HCD signal 44 can also couple onto other twisted wire pairs inthe binder group 30 and be received by other transceivers. For example,if a transceiver 50 (shown in shadow) is connected to another twistedwire pair 34 in the binder group 30, that transceiver 50 also receivesan HCD signal 46′ by the electromagnetic coupling 62′ of the signal 44onto that twisted pair 34. The transceiver 50 may recognize and respondto the HCD signal 46′ just as the HPN transceivers 21 recognize andrespond to the HCD signal 46.

[0032] The transceiver 50′ connected to the DSL device 41 by the twistedpair 33 also receives the signal 44. Normally, the signal 44 indicatesto a receiving transceiver that the transceiver is producing anunacceptable level of interference and should perform actions to reducethe interference. In this case, however, the receiving transceiver 50′does not recognize the signal 44 because the signal 44 hascharacteristics, such as for example, a predetermined frequency, thatthe transceiver 50′ is not using to communicate with the DSL device 41.Thus, the signal 44, when received, does not induce a response from thetransceiver 50′.

[0033]FIG. 4 is a flow chart illustrating an embodiment of a processused by the HPN transceivers 21 and the DSL device 41 to decrease thecrosstalk 31 to an acceptable level (i.e., below the predeterminedthreshold discussed above). The DSL transceiver 41 first detects (step101) a high level of crosstalk 31 produced by the HPN transceiver 21.The DSL device 41 determines if the high level is unacceptable based onthe predetermined threshold. If the DSL device 41 determines that thecrosstalk 31 level is unacceptable, the DSL device 41 sends (step 102)the HCD signal 44 to communicate with the HPN transceivers 21. The HCDsignal 44 is electromagnetically coupled onto the twisted pair 32 toform the electromagnetically coupled signal 46 (as described above). TheHPN transceiver 21 detects (step 103) the electromagnetically coupledsignal 46.

[0034] The HPN transceiver 21 then determines (step 104) if the HPNtransceiver 21 can take action to adjust the level of crosstalk 31, suchas by decreasing the transmission power of the HPN signals 26transmitted by the HPN transceiver 21. If the HPN transceiver 21 isunable to take an action that has the effect of decreasing oreliminating the crosstalk 31, then the HPN transceiver 21 notifies (step200) the user of the HPN transceiver 21 that a filter should beinstalled. Any notification to the user will suffice. For example, theHPN transceiver 21 can display a notification on a user interface on acomputer screen to inform the user that the filter is necessary tocontinue operation of the HPN transceiver 21. The user should installthe filter in a position in the home 20 so that the noise produced byall HPN signals 26 is filtered before exiting the home 20. One exampleof a location for filter installation is a network interface deviceQNTID) point 48 (shown in FIG. 3).

[0035] If the HPN transceiver 21 determines that a reduction in thetransmission power is possible, then the HPN transceiver 21 reduces(step 105) the transmission power by a predetermined amount (e.g., 2dB). Each time the HPN transceiver 21 receives the electromagneticallycoupled signal 46 and detects that the transmission power can bereduced, the HPN transceiver 21 reduces the transmission power by thepredetermined amount. In another embodiment, the amount of reduction isdetermined based on the level of crosstalk 31 relative to thepredetermined threshold.

[0036] In another embodiment, the HPN transceiver 21 decreases the levelof crosstalk 31 by transmitting the HPN signals 26 at a differentfrequency. In yet another embodiment, the HPN transceiver 21 decreasesthe crosstalk 31 level by transmitting the HPN signals 26 at shortertime increments. In a further embodiment, the HPN transceiver 21decreases the crosstalk 31 level using a combination of the abovetechniques (e.g., decreasing transmission power, changing the frequencyof the HPN signals 26, and transmitting the HPN signals 26 at shortertime increments).

[0037] After the HPN device 41 acts to decrease the crosstalk 31 level,the DSL device 41 detects (step 106) the decrease and determines (step106) if the crosstalk 31 is at an acceptable level. If the crosstalk 31is at an acceptable level, the DSL device 41 stops transmitting (step107) the HCD signal 44. By stopping transmission of the HCD signal 44,the HPN transceivers 21 are notified that the adjustment in thetransmission power level was sufficient and the HPN transceiver 21operates (step 108) at the reduced power level.

[0038] In another embodiment, when the DSL device 41 determines that thelevel of crosstalk 31 is acceptable, the DSL device 41 sends (shadowstep 107A) a new HCD signal (HCD2) having different characteristics,such as frequency and/or modulation type, than the HCD signal 44. Inthis case the HPN transceiver 21 detects (step 108) the HCD2 signal andproceeds to operate at the new decreased power level.

[0039] If the DSL device 41 determines that the crosstalk 31 is not atan acceptable level, the DSL device 41 repeatedly sends (step 102) theHCD signal 44. The HPN transceiver 21 and the DSL device 41 will repeatthe steps listed above (steps 102 through 106) until the DSL device 41determines that the crosstalk 31 is at an acceptable level.

[0040] While the invention has been shown and described with referenceto specific preferred embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the following claims. For example, in other embodiments theDSL device 41 can issue the HCD communication signal 44 for a variety ofpurposes unrelated to the detection of interference, or in response todetecting other types of interference or disturbance events (i.e., otherthan crosstalk), without departing from the principles of the invention.

1. A method for a transceiver to communicate over a wire in a group ofwires comprising: receiving communications over a first wire;transmitting over the first wire a communication signal thatelectromagnetically couples to a second wire to produce anelectromagnetically coupled signal on the second wire; and conveying amessage, by the electromagnetically coupled signal, that induces aresponse from a second transceiver connected to the second wire.
 2. Themethod of claim 1 wherein the conveyed message directs the secondtransceiver to alter an operation of the second transceiver.
 3. Themethod of claim 1 wherein the conveyed message requests that the secondtransceiver make an adjustment to a transmission parameter used totransmit information over the second wire.
 4. The method of claim 1wherein the communication signal has a predefined frequency and apredefined phase characteristic.
 5. The method of claim 3 furthercomprising detecting interference on the communications received overthe first wire, and wherein the transmitting of the communication signaloccurs in response to detecting the interference.
 6. The method of claim5 wherein the transmitting of the communication signal occurs if thedetected interference exceeds a predetermined threshold.
 7. The methodof claim 5 further comprising ceasing transmission of the communicationsignal if the detected interference is below a predetermined threshold.8. The method of claim 5 wherein the interference is crosstalk.
 9. Themethod of claim 5 wherein the adjustment reduces the interferencedetected on the first wire.
 10. A method of communicating between afirst and a second transceiver that are connected to different wires ina group of wires and that are unconnected to each other by any wire inthe group of wires, the method comprising: transmitting signals by afirst transceiver over a first wire; receiving a communication signalover the first wire transmitted from a second transceiver over to asecond wire and electromagnetically coupled to the first wire from thesecond wire; and performing an action in response to a message conveyedby the electromagnetically coupled communication signal.
 11. The methodof claim 10 wherein the performed action is an adjustment to atransmission parameter.
 12. The method of claim 11 wherein theadjustment changes a power level used to transmit signals over the firstwire.
 13. The method of claim 12 wherein the changing of the power levelreduces the power level used to transmit signals over the first wire.14. The method of claim 11 wherein the adjustment changes a frequencyband used to transmit signals over the first wire.
 15. The method ofclaim 11 wherein the adjustment changes time increments used to transmitsignals over the first wire.
 16. The method of claim 15 wherein thechanging of the time increments reduces the time increments used totransmit signals over the first wire.
 17. The method of claim 10 whereinthe transmitting of the signals over the first wire producesinterference on the second wire.
 18. The method of claim 17 wherein theinterference is crosstalk.